This invention relates to so-called "round balers" which are balers operable to produce cylindrical or "round" rolls or bales of crop material. More particularly, the invention is concerned with apparatus for controlling the wrapping of a round bale with wrapping material.
When round balers first were introduced in the agricultural market, they were equipped with wrapping devices operable to wrap a completed bale with twine such as has been used for many years to wrap the traditional square or rectangular bale of crop material. Subsequently, round bales were wrapped with sheet material and more recently, with relatively large mesh netting. The use of sheet material or netting brought about the introduction of relatively sophisticated control mechanisms for the bale wrapping operation in order to control comparatively accurately the length of wrapping material dispensed for each bale so as to minimise the use and expense thereof. These sophisticated control mechanisms have to a great extent involved electronic and/or electro-mechanical arrangements with a relatively high initial cost and causing problems as regards maintenance in the field.
Less sophisticated mechanical systems have accordingly been proposed to overcome the above problems but these have proved unsatisfactory for other reasons For example, U.S. Pat. No. 4,604,855 discloses wrapping apparatus for a round baler in which the bale wrapping operation is initiated by pulling on a lever with a rope or wire, the resulting pivotal movement of the lever serving both to raise cutter means and to initiate drive to a feed mechanism for the wrapping material. At the same time a mechanism for "timing" the feeding of wrapping material, and hence the length thereof dispensed, is primed. The disadvantages of this arrangement are that the cutter means has to be raised manually, requiring considerable force because of the inevitably heavyweight nature thereof to ensure cutting of the wrapping material on release, and that a certain force is also required to maintain engagement between a pair of friction rolls, one of which drives one of a pair of feed rolls for the wrapping material. The operator only releases his pull on the rope or wire when the wrapping material reaches the bale chamber in which the completed bale to be wrapped is rotating, whereupon the dispensing of the wrapping material from a source roll is taken over solely by the rotating bale, the friction drive ceasing on release of the wire or rope. The primed "timing" mechanism is then activated and operates to release the cutter means when the mechanism times out, whereby the wrapping material is cut and continued rotation of the bale takes up the remainder of the cut length. Thus with this arrangement, the satisfactory actuation of the wrapping apparatus is very dependent on the pull exerted by the baler operator on the wire or rope and the ability of the operator to judge when the wrapping material is in the correct position relative to the bale to be wrapped. Accordingly, the likelihood of mis-wrapping is unacceptably high.
In German Patent No. 3,418,681 there is disclosed a generally similar wrapping apparatus in that the pulling on a rope or wire by the operator raises or pivots cutter means ready for the subsequent cutting action and engages a drive mechanism which "times" the wrapping operation. Although in this arrangement the operator does not have to maintain the pull on the wire or rope to ensure that the feed mechanism for the wrapping material is actuated and then watch for when the wrapping material is in position for being taken up by the rotating bale to be wrapped, the arrangement still suffers from the disadvantage that heavy cutter means has to be raised manually.
In both of the known arrangements described above, the cutter means is primed for cutting on initiation of the wrapping sequence, whereby the cutter means are in the normal rest position which is not the case in the arrangement of European Application No. 0.239.761 in which the cutter means are primed as a wrapped bale is discharged from the baler and remain so until released at the end of the wrapping sequence. Thus the cutter means is not primed manually but the arrangement suffers from the disadvantage that the cutter means can be released inadvertently during normal operation of the baler or during baler maintenance which is highly undesirable.